1. Field of the Invention
The present invention relates to apparatuses used to carry out methods for guiding aquatic crustaceans' locomotive orientation with their innate biological tendency responding to specific contrasts of bright and dark. These apparatuses provide such visual effect of bright and dark contrasts at a predetermined area within these crustaceans' residing water body to initiate their move toward the predetermined areas for staying or hiding.
2. Description of Related Art
Aquatic crustaceans are important economic aquatic animals. People usually obtain those animals by harvesting them from nature environment directly or by artificial cultivation. Many countries have paid great attention to focus on this artificial cultivation. Traditionally, such artificial cultivation (named aquaculture) makes use of wide expanse of land and ponds with natural water supply. Recently, several automated high-density culturing systems have been disclosed. These systems use water recirculation equipments and filtering apparatuses to curtail both the consumption of water and land resources and the damages to the natural environment, like U.S. Pat. Nos. 4,368,691, 4,446,025 and 5,961,831. High-density cultivation system can bring larger margin but draw simultaneously a crisis to increase the production loss resulting from cannibalization which counteracts the profits. This loss is derived from different feeding and moving ability in different staged crustaceans, ex. molted or immature crustaceans are usually vulnerable to adult ones within the same body of water. This is the bottleneck in the efforts to elevate the culturing density and hence further increase its profits as well.
The behavioral management technique in maintaining cultivated aquatic crustaceans, for the purposes of reducing cannibalistic activities and other, is thus an important task in above-said systems and other ways for culturing aquatic crustaceans. Several means to attract aquatic crustaceans' active moving are employed attempting to increase the harvesting efficiency. Traditional scent/taste attractants are commonly used to implement the management of these feeding, breeding and hatching behaviors. U.S. Pat. No. 5,706,759 discloses a process to investigate potential chemo-stimulants, chemo-repelling agents or chemo-attractants for shrimps, but it still lacks further practical techniques for specific behavioral management. A kind of bait fluid, such as fish oil, is used in U.S. Pat. No. 4,828,829 only for harvesting crab with expected higher efficiency. A food-luring trapper using an attractor to attract plankton or other similar shrimp food organisms is designed to allure and catch shrimps (U.S. Pat. No. 5,259,809). No other successful methods for managing the motion of aquatic crustaceans in the light of their biological responses reacting to bright and dark visual stimuli have been developed previously.
Due to the lack of proper techniques for culturing and managing aquatic crustaceans, the culture density is always maintained as a balance between cannibalization and growth, and, in shrimp, the culture pond or tank is always kept in certain water depth, at about 0.6 to 2.0 meter, in order to reduce the incidence of cannibalizing behavior basing on the behavior that newly molted shrimp jump back or up away in order to escape from the attack of other non-molted shrimp mates. The water body with 0.6 to 2.0 meter depth has too large a mass to enable the development of multi-layered culture system and thus the traditional culturing system is restricted to planar installation.
In other fields, laboratories, with crustaceans cultivated in controlled environments for research, and markets like restaurants and pet stores, with crustaceans kept in tight space for display, all face the same problems in behavioral management of aquatic crustaceans and are unable to maintain or display living crustaceans effectively in desired manners.
In nature, many aquatic crustaceans, such as shrimps, inhabit in water environments with bright-dark alternating or contrasting light effects appearing as wavy light reflections in shelters and crevices but not in open fields. Crustaceans may use these light effects to aim for a potential hiding place. Once arriving to the location, they may use their other senses, such as tactile senses, to decide if they would take the action of hiding or go for another potential location.
Propensity to react to the bright and dark visual stimuli in aquatic crustaceans is a unique nature which can be used in a feasible means to guide their motion and localization. The present invention for guiding aquatic crustaceans is centered upon the aforesaid biological tendency. This tendency responding to bright and dark contrast, however, is not unique for just crustaceans as it can be found in other animals, like insects. No practical concepts in the prior art, however, are disclosed as an efficient and effective process for guiding aquatic crustaceans' motion related to the techniques used in the present invention.